[PATCH v3 3/5] x86/mwait-idle: add AlderLake support

[Jan Beulich <jbeulich@xxxxxxxx>]

From: Zhang Rui <rui.zhang@xxxxxxxxx>

Similar to SPR, the C1 and C1E states on ADL are mutually exclusive.
Only one of them can be enabled at a time.

But contrast to SPR, which usually has a strong latency requirement
as a Xeon processor, C1E is preferred on ADL for better energy
efficiency.

Add custom C-state tables for ADL with both C1 and C1E, and

 1. Enable the "C1E promotion" bit in MSR_IA32_POWER_CTL and mark C1
    with the CPUIDLE_FLAG_UNUSABLE flag, so C1 is not available by
    default.

 2. Add support for the "preferred_cstates" module parameter, so that
    users can choose to use C1 instead of C1E by booting with
    "intel_idle.preferred_cstates=2".

Separate custom C-state tables are introduced for the ADL mobile and
desktop processors, because of the exit latency differences between
these two variants, especially with respect to PC10.

Signed-off-by: Zhang Rui <rui.zhang@xxxxxxxxx>
[ rjw: Changelog edits, code rearrangement ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Origin: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 
d1cf8bbfed1e
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
v3: New.

--- a/xen/arch/x86/cpu/mwait-idle.c
+++ b/xen/arch/x86/cpu/mwait-idle.c
@@ -606,6 +606,84 @@ static const struct cpuidle_state icx_cs
 };
 
 /*
+ * On AlderLake C1 has to be disabled if C1E is enabled, and vice versa.
+ * C1E is enabled only if "C1E promotion" bit is set in MSR_IA32_POWER_CTL.
+ * But in this case there is effectively no C1, because C1 requests are
+ * promoted to C1E. If the "C1E promotion" bit is cleared, then both C1
+ * and C1E requests end up with C1, so there is effectively no C1E.
+ *
+ * By default we enable C1E and disable C1 by marking it with
+ * 'CPUIDLE_FLAG_DISABLED'.
+ */
+static struct cpuidle_state __read_mostly adl_cstates[] = {
+       {
+               .name = "C1",
+               .flags = MWAIT2flg(0x00) | CPUIDLE_FLAG_DISABLED,
+               .exit_latency = 1,
+               .target_residency = 1,
+       },
+       {
+               .name = "C1E",
+               .flags = MWAIT2flg(0x01),
+               .exit_latency = 2,
+               .target_residency = 4,
+       },
+       {
+               .name = "C6",
+               .flags = MWAIT2flg(0x20) | CPUIDLE_FLAG_TLB_FLUSHED,
+               .exit_latency = 220,
+               .target_residency = 600,
+       },
+       {
+               .name = "C8",
+               .flags = MWAIT2flg(0x40) | CPUIDLE_FLAG_TLB_FLUSHED,
+               .exit_latency = 280,
+               .target_residency = 800,
+       },
+       {
+               .name = "C10",
+               .flags = MWAIT2flg(0x60) | CPUIDLE_FLAG_TLB_FLUSHED,
+               .exit_latency = 680,
+               .target_residency = 2000,
+       },
+       {}
+};
+
+static struct cpuidle_state __read_mostly adl_l_cstates[] = {
+       {
+               .name = "C1",
+               .flags = MWAIT2flg(0x00) | CPUIDLE_FLAG_DISABLED,
+               .exit_latency = 1,
+               .target_residency = 1,
+       },
+       {
+               .name = "C1E",
+               .flags = MWAIT2flg(0x01),
+               .exit_latency = 2,
+               .target_residency = 4,
+       },
+       {
+               .name = "C6",
+               .flags = MWAIT2flg(0x20) | CPUIDLE_FLAG_TLB_FLUSHED,
+               .exit_latency = 170,
+               .target_residency = 500,
+       },
+       {
+               .name = "C8",
+               .flags = MWAIT2flg(0x40) | CPUIDLE_FLAG_TLB_FLUSHED,
+               .exit_latency = 200,
+               .target_residency = 600,
+       },
+       {
+               .name = "C10",
+               .flags = MWAIT2flg(0x60) | CPUIDLE_FLAG_TLB_FLUSHED,
+               .exit_latency = 230,
+               .target_residency = 700,
+       },
+       {}
+};
+
+/*
  * On Sapphire Rapids Xeon C1 has to be disabled if C1E is enabled, and vice
  * versa. On SPR C1E is enabled only if "C1E promotion" bit is set in
  * MSR_IA32_POWER_CTL. But in this case there effectively no C1, because C1
@@ -1032,6 +1110,14 @@ static const struct idle_cpu idle_cpu_ic
        .c1e_promotion = C1E_PROMOTION_DISABLE,
 };
 
+static struct idle_cpu __read_mostly idle_cpu_adl = {
+       .state_table = adl_cstates,
+};
+
+static struct idle_cpu __read_mostly idle_cpu_adl_l = {
+       .state_table = adl_l_cstates,
+};
+
 static struct idle_cpu __read_mostly idle_cpu_spr = {
        .state_table = spr_cstates,
        .c1e_promotion = C1E_PROMOTION_DISABLE,
@@ -1099,6 +1185,8 @@ static const struct x86_cpu_id intel_idl
        ICPU(SKYLAKE_X,                 skx),
        ICPU(ICELAKE_X,                 icx),
        ICPU(ICELAKE_D,                 icx),
+       ICPU(ALDERLAKE,                 adl),
+       ICPU(ALDERLAKE_L,               adl_l),
        ICPU(SAPPHIRERAPIDS_X,          spr),
        ICPU(XEON_PHI_KNL,              knl),
        ICPU(XEON_PHI_KNM,              knl),
@@ -1269,6 +1357,30 @@ static void __init skx_idle_state_table_
 }
 
 /*
+ * adl_idle_state_table_update - Adjust AlderLake idle states table.
+ */
+static void __init adl_idle_state_table_update(void)
+{
+       /* Check if user prefers C1 over C1E. */
+       if ((preferred_states_mask & BIT(1, U)) &&
+           !(preferred_states_mask & BIT(2, U))) {
+               adl_cstates[0].flags &= ~CPUIDLE_FLAG_DISABLED;
+               adl_cstates[1].flags |= CPUIDLE_FLAG_DISABLED;
+               adl_l_cstates[0].flags &= ~CPUIDLE_FLAG_DISABLED;
+               adl_l_cstates[1].flags |= CPUIDLE_FLAG_DISABLED;
+
+               /* Disable C1E by clearing the "C1E promotion" bit. */
+               idle_cpu_adl.c1e_promotion = C1E_PROMOTION_DISABLE;
+               idle_cpu_adl_l.c1e_promotion = C1E_PROMOTION_DISABLE;
+               return;
+       }
+
+       /* Make sure C1E is enabled by default */
+       idle_cpu_adl.c1e_promotion = C1E_PROMOTION_ENABLE;
+       idle_cpu_adl_l.c1e_promotion = C1E_PROMOTION_ENABLE;
+}
+
+/*
  * spr_idle_state_table_update - Adjust Sapphire Rapids idle states table.
  */
 static void __init spr_idle_state_table_update(void)
@@ -1324,6 +1436,10 @@ static void __init mwait_idle_state_tabl
        case INTEL_FAM6_SAPPHIRERAPIDS_X:
                spr_idle_state_table_update();
                break;
+       case INTEL_FAM6_ALDERLAKE:
+       case INTEL_FAM6_ALDERLAKE_L:
+               adl_idle_state_table_update();
+               break;
        }
 }